Part of a vineyard at the Beaver Creek Winery destroyed over the weekend in Middletown, California.
Photograph: John G Mabanglo/EPA

The wildfires burning across California are threatening wineries and vineyards across the region at the start of harvest season, posing a potential risk to the state’s lucrative wine industry.

The fire in Lake County in northern California, less than 20 minutes from the heart of America’s wine country of Napa and Sonoma, had reached 73,000 acres and was 35% contained by Thursday, according to the California department of forestry and fire protection (Cal Fire). Approximately 600 homes are destroyed, at least three people have died and others are missing as a result of the blaze.

Some vineyards in the region are currently inaccessible due to evacuation orders established by Cal Fire.

Steve Tylicki of Steele Wines in Kelseyville said the biggest obstacle facing vineyards and wineries are the road closures and whether grapes remain on the vine. “I know of some vineyards that still have 80% of their grapes on the vine and they can’t get in to irrigate, which could be problematic,” he said. Steele Wines has already harvested “well over 80%” of its grapes.

There is the potential of grapes becoming overripe and potentially unusable, he added.

A plowed up grape vineyard near Fresno, California, in the Central Valley. Photograph: Michael Nelson/EPA

Driving from Calistoga north towards Middletown, Hidden Valley, Cobb and other towns,where around 1,000 evacuees have fled, blackened vines are visible.

Some wineries confirmed that they were closely watching Cal Fire maps of areas affected by the fires, hoping that their vineyards are not hit by flames. “One to two days is OK, but if it continues for a while you never know what the state of the grapes will be,” Tylicki added.

Wildfires have hit California hard this year. Tens of thousands of acreage has burned, destroying hundreds of homes. The smoke, which is immediately in the taste of visitors to the affected region, could also pose a problem to grapes: in August, a number of vineyards sent their fruit to laboratories to test if the smoke amid concerns it would have an adverse affect on the taste of their wine.

California produces around 60% of American wine, according to the Wine Institute, and with sales topping $24m last year.

According to the Lake County Wine Industry, at least one winery in Middletown was destroyed by the recent fire that hit on Saturday. “We do have inventory in the warehouse to keep our orders filled and our tasting room stocked,” Michael and Adawn Woods were quoted as saying. Shed Horn Cellars produces approximately 3,000 cases of wine annually. It is unclear how they will recover for next year’s harvest.

Wineries and vineyards are unlikely to know the full extent of the damage and the potential issues that could arise from a reduced harvest until the fires subside. For now at least, the cost of bottles of California wine are not expected to change.

This article was amended on 26 May 2016 as a result of a fact-checking investigation. A quote was removed after a source denied having spoken to the reporter. This article was amended further to correct the percentage of US wine produced in California from 90% to 60%. California produces 90% of US wine exports.